Neural stimulation has been proposed as a therapy to treat hypertension, also referred to as high blood pressure. It has been proposed that electrical stimulation directed at baroreceptor regions can be used to induce a baroreceptor reflex (baroreflex) that reduces blood pressure. Through the negative feedback loop of the baroreflex, the central nervous system regulates the blood pressure to maintain the blood pressure at a relatively stable level. For example, high blood pressure that causes arterial stretching activates baroreceptors to send nerve impulses to the brain and, in response, the brain controls the pumping activity of the heart and blood vessel dilation to reduce the blood pressure.
The change in the blood pressure that is due to electrical stimulation of a site in a baroreceptor region fluctuates dramatically based on the location of the site in the baroreceptor region, i.e., the change in the blood pressure due to the stimulation at a first site in the baroreceptor region can be significantly different than the change in the blood pressure due to the stimulation at a second site in the baroreceptor region. Animal experiments indicate that stimulation sites separated by less than 1 millimeter (mm) can produce dramatically different changes in the blood pressure. Thus, the implantation of a stimulation device on a baroreceptor region usually requires extensive mapping of the region to find a location that provides effective or the most effective control of the blood pressure.
Often, surgeons manually hold one or more electrodes at various locations on the baroreceptor region to map the region during an implantation procedure. Mapping the baroreceptor region takes significant time and effort due to the difficulty of manually positioning the electrode at a site, stimulating the baroreceptor region at the site, waiting for the change in the blood pressure, measuring the change in the blood pressure, and letting the blood pressure return to a steady level before positioning the electrode at the next site and repeating the process. Longer procedure times increase the risk to a patient and lead to physician fatigue and dissatisfaction. In addition, this manual procedure can introduce mechanical activation of the baroreceptors, which hinders the evaluation of the change in the blood pressure that is due to the electrical stimulation. As a result, full mapping of the baroreceptor region is often not obtained, which can result in sub-optimal implant location, sub-optimal stimulation therapy, and, over time, loss of therapeutic value.